The invention relates to a load-disconnecting switch, in particular for the load circuit of a vehicle battery, in which the load circuit can be disconnected automatically via an electromagnet system.
In motor vehicles, it is desirable in specific disturbance situations to disconnect the on-board network to a dead state abruptly. Such cases are, for example, a short in the load circuit that may lead to battery discharge or vehicle burning, wrong polarization in the event of starting aid which may cause damage to the battery, but also destruction of the electronic systems in the on-board network, or a collision accident which may also cause shorts with a resulting risk of burning.
The document DE 41 10 240 C1 already discloses a means for providing protection to a main current path in a motor vehicle. A disconnect situation is determined by various sensors and comparison means and evaluated for disconnecting the circuit. This document mentions as disconnect means, for example, an explosive cap or an electromagnetic actuator, without the construction and function of such an actuator being discussed in more detail.
The document DE 197 01 933 C1 reveals a load-disconnecting switch for the load circuit of a vehicle battery, in which a contact arrangement is connected between a pole terminal and a load circuit. In case of occurrence of a disturbance situation, the contact arrangement is unlocked via an electromagnet system and the circuit is interrupted. This known load-disconnecting switch comprises an arrangement having a contact rocker with a comparatively large number of individual parts necessitating corresponding manufacturing expenditure and volume.
It is the object of the present invention to provide a load-disconnecting switch that is of simple construction, does not switch unintentionally even in case of high accelerations and is of low volume.
According to the invention, this object is met with a load-disconnecting switch comprising:
a housing having a base and a housing cover,
a magnet system having a coil, a core arrangement and an armature, the core arrangement having a permanent-magnetic section exerting a holding force through which the armature is attracted to pole areas of the core arrangement, and said magnet system being adapted to be excited contrary to said permanent-magnetic section,
an armature spring biasing the armature to an open position, with the holding force of the permanent-magnetic section with attracted armature being higher than the spring force of the armature spring,
a contact system having a contact spring, a switching contact arranged on the contact spring and a fixed contact cooperating with the switching contact,
first and second connecting conductors extending out of said housing for connection of the switching contact and the fixed contact.
An essential element of the load-disconnecting switch is the permanent-magnetic section of the core arrangement. It has the effect that the magnetic circuit has an attracted armature in the rest state and, thus, has no movable parts in the rest state having no holding force applied thereto. This has the advantage that the construction provides particular strength with respect to acceleration. In case of use as a battery disconnecting switch in a motor vehicle, it is ensured that also in case of high acceleration forces, e.g. in an accident situation, the load-disconnecting switch is not triggered prior to the airbag. Moreover, in case of accidental dropping during assembly, the risk of damage to the movable parts is reduced. Electric excitation of the coil causes release of the armature, since the excited coil generates a magnetic flux opposite to the magnetic flux generated by the permanent magnet. Consequently, the matching spring force of an armature spring is sufficient for opening the armature. The use of a permanent magnet as holding member permits the necessary driving power to be kept very low. In this manner, it is possible to realize a particularly compact constructional volume.
In an advantageous embodiment, additional mechanical locking is provided. The necessary release force may thus be reduced further. In addition thereto, this locking provides for increased strength with respect to acceleration.
In a preferred embodiment, the armature spring has an extension in the form of a spring clip realizing a manual closing and release button. It is expedient in this respect when the spring clip extends along an outside of the housing cover. It is particularly advantageous when the housing cover is resilient in specific portions so that a force can be exerted on the spring clip from outside of the housing.
Further details and developments of the invention are indicated in the dependent claims.